Techniques of recognizing an object on the basis of the similarity of a visual feature are known. For example, techniques of recognizing a person by using an image of biological information such as a face and a fingerprint have been developed for the purpose of administration and the like.
In such recognition techniques, typically, the feature of an image registered in advance and referred to as dictionary data is compared with the feature of an inputted image so that one having the highest similarity in the feature or alternatively having a similarity exceeding a predetermined threshold is judged as an image of the corresponding object. In particular, in a case that the visual feature of an object can suffer a temporal change like in a case that a person is to be recognized by using a face image, for the purpose of improving the recognition accuracy also against a temporal change, techniques of performing addition or update by using the inputted data as registered data have been proposed.
For example, Patent Document 1 and Patent Document 2 disclose techniques of, in accordance with the magnitude of the similarity in the feature between an inputted image and an image recognized as an object, adding the inputted image as registered data. Further, Patent Document 3 discloses a technique of, in accordance with the number of times of input of an input image performed until the authenticating processing becomes successful or alternatively in accordance with the time having elapsed since the last date of update of the dictionary, updating the dictionary by using the input image as new registered data.